The invention relates to a method of fabricating a semiconductor device and, more particularly, to a method of fabricating patterns in a semiconductor device using a spacer.
In general, a plurality of devices constituting a semiconductor device, for example, an active device such as a transistor or a passive device such as a register, have been embodied in the form of patterns. For example, the transistor has a structure including a gate insulating layer and a gate electrode layer that are disposed on a semiconductor substrate. In particular, the gate insulating layer and the gate electrode layer have a predetermined pattern structure, such as a stripe.
A photolithography process is generally used to form the patterns. That is, a photoresist layer pattern is formed on a target layer to be patterned, and an exposed portion of the target layer is removed through an etching process using the photoresist layer pattern as an etching mask, thereby obtaining a required pattern. However, with increasing levels of integration, the above method becomes more limited. Specifically, although the pitch of the patterns decreases as the semiconductor device becomes more highly integrated, the photolithography process technology does not keep pace with the decrease of the pattern pitch due to its basic limitation.
Accordingly, a method for fabricating the patterns using spacers has been suggested to form patterns having micro pitches. According to this method, a sacrificial layer pattern is formed on a target layer to be formed with the patterns, and the spacers are formed on sidewalls of the sacrificial layer pattern. Then, the sacrificial layer pattern is removed and an exposed portion of the target layer is removed through an etching process using the spacers as an etching mask. In general, the spacers can be formed with a sufficient thickness and the thickness of the spacers can be easily controlled. Thus, the patterns having micro pitches can be formed by using the spacers. However, because the spacers are formed at the same time, the spacers have the same thickness throughout the entire region. Accordingly, the patterns have the same pitch. However, it is often desirable to form patterns having different pitches using a single patterning process. In such a case, an additional mask process must be performed to form the variable-pitch patterns.